1. Field of the Invention
The technical field relates to a power receiving device of a capacitive coupling type and a capacitive coupling type wireless power feed system.
2. Description of the Related Art
In recent years, electronic devices using electric power as a prime mover, which are typified by mobile devices such as mobile phones or laptop personal computers, are often used while being carried. In addition, transportation means such as bicycles and automobiles which use electric power as a prime mover have been developed in terms of its cleanness and safety in the aspect of environment.
Electronic devices and transportation means which are used outside the house, for example in a travel destination, or which are used while traveling are difficult to receive electric power constantly with a wire from a commercial power supply distributed to each house. Therefore, portable electronic devices and transportation means incorporate batteries which have been charged from a commercial power supply in advance and operate by receiving electric power from the batteries.
Since the operating time of the electronic device is limited by the amount of power storage of the battery, a user needs to prepare a spare battery or search a commercial power supply in the travel destination by which the battery can be recharged in order to use the electronic device continuously for a long time. In view of the above, a contactless type power feed system has been suggested so that power can be fed to the battery even when there is no commercial power supply.
As the contactless type power feed system, there are an electromagnetic induction type, an electromagnetic wave transmission type, an electromagnetic field resonance type, an electric field coupling type, and the like.
In the electromagnetic induction type, current is fed to one of coils which are adjacent to each other to generate a magnetic flux so that an electromotive force is generated to the other coil via the magnetic flux. In the electromagnetic wave transmission type, supplied electric power is converted into an electromagnetic wave to be transmitted as a microwave or the like via an antenna. In the electromagnetic field resonance type, a resonance phenomenon of an electromagnetic wave is utilized.
Further, in the electric field coupling type, which is also called a capacitive coupling type, each of a device on a power transmitting side and a device on a power receiving side is provided with an electrode and electric power is transmitted utilizing an electric field generated between the electrodes. The electric field coupling type has attracted attention in point of having high transmission efficiency and a relatively wide margin on the position where the device on the power receiving side is located.
As the electric field coupling type power feed system, for example, Patent Document 1 has disclosed an apparatus in which electricity is delivered via an inductive substance. In the apparatus disclosed in Patent Document 1, as shown in FIG. 5, a high-voltage high-frequency generator 501 has one terminal connected to a passive electrode 502 and the other terminal connected to an active electrode 503 (also called “generator electrode”). The active electrode 503 is smaller than the passive electrode 502. Moreover, the active electrode 503 generates a zone 504 as an intense field where energy is concentrated.
A high-voltage high-frequency load 505 is connected on one side to an electrode 506 (also called “electromotive electrode”) and on the other side to an electrode 507 (also called “passive electrode”). The electrode 506 is located in the zone 504 as the intense field.
Further, in the electric field coupling type power feed system, a high-frequency noise sometimes causes electrostatic breakdown or malfunction of a power receiving device or a power transmitting device. As the high-frequency noise, for example, electrostatic discharge (ESD), an electromagnetic wave existing in the atmosphere, or the like is given.
Therefore, as a method for suppressing the influence of the high-frequency noise, a power receiving device or a power transmitting device of a power feed system is sometimes provided with a filter for blocking the high-frequency noise.
[Reference]
[Patent Document 1]
Japanese Translation of PCT International Application No. 2009-531009